Some slight archaeological evidence shows communities of hunter-gatherers inhabited Cambodia during Holocene: the most ancient Cambodian archeological site is considered to be the cave ofL'aang Spean, in Battambang Province, which belongs to the so-called Hoabinhian period. Excavations in its lower layers produced a series of radiocarbon dates as of 6000 BC.[9][10]

Upper layers in the same site gave evidence of transition to Neolithic, containing the earliest dated earthenware ceramics in Cambodia[11]

Archeological records for the period between Holocene and Iron Age remain equally limited. Other prehistoric sites of somewhat uncertain date are Samrong Sen (not far from the ancient capital ofUdong), where the first investigations began in 1877,[12] and Phum Snay, in the northern province of Banteay Meanchey.[13] Prehistoric artifacts are often found during mining activities inRatanakiri.[9]

The most outstanding prehistoric evidence in Cambodia however are probably various "circularearthworks", discovered in the red soils near Memot and in the adjacent region of Vietnam as of the end of the 1950s. Their function and age are still debated, but some of them possibly date from 2nd millennium BC at least.[14][15]

A pivotal event in Cambodian prehistory was the slow penetration of the first rice farmers from the north, which began in the late 3rd millennium BC.[16]

Iron was worked by about 500 BC, with supporting evidence coming from the Khorat Plateau, in modern day Thailand. In Cambodia, some Iron Age settlements were found beneath Angkorian temples, like Baksei Chamkrong. Others were circular earthworks, like Lovea, a few kilometers north-west of Angkor. Burials, much richer, testify to improvement of food availability and trade (even on long distances: in the 4th century BC trade relations with India were already opened) and the existence of a social structure and labor organization.[16]